Time comparator or drier control



y 1963 N. J. PANSING ETAL 3,088,221

TIME COMPARATOR OR DRIER CONTROL Filed June 29, 1959 6 Sheets-Sheet 1 1//V 11 INVENTORS )7e/son J. P421593 Geo ye B. 10159 THf/R A TURNEY May 7,1963 N. J. PANSING ETA]. 3,088,221

TIME COMPARATOR OR DRIER CONTROL Filed June 29, 1959 6 Sheets5heet 2 NINVENTORS )7e/so27 J. P0225112 ii: 3 Geo ye B. 105

May 7, -1983 N. J. PANSING ETAL TIME COMPARATOR OR DRIER CONTROL 6Sheets-Sheet 3 Filed June 29, 1959 INVENTORS )7e/son J. P42751233 'eorye5. [any *z 7' 51k ZTORNE May 7, 1963 Filed June 29, 1959 N. J. PANSINGEIAL TIME COMPARATOR OR DRIER CONTROL 6 Sheets-Sheet 4 l j---m QINVENTORS )7e/son J. an sigg 'eorqe 5. 10229 HEIR ATTORNEV May 7, 1963N. J. PANSING ETAL TIME COMPARATOR oR DRIER CONTROL 6 Sheets-Sheet 5Filed June 29, 1959 INVENTORS )7e/son J. Pansz'gq 6y Geogqe ,5. [039 f111% firm/45 May 7, 1963 N. J. PANSING EI'AL TIME COMPARATOR OR DRIERCONTROL Filed June 29, 1959 6 Sheets-Sheet 6 )Ze/son J. Pansizzy G'earye5. [any M TTORIVEY United States Patent 3,088,221 TIME COMPARATOR ORDRIER CONTROL Nelson J. Pansing and George B. Long, Dayton, Ohio,assignors to General Motors Corporation, Detroit, Mich, a corporation ofDelaware Filed June 29, 1959, Ser. No. 823,7 63 16 Claims. (Cl. 34-45)This invention relates to a domestic appliance and more particularly toan improved clothes dryer.

Considerable effort has been expended in the art of domestic clothesdryers to obtain a drying system which will automatically terminate whenthe clothes are dried to the point at which they contain the properamount of moistureneither under-dried nor over-dried. Close control ofthe end point dryness in a clothes dryer has not been solved in theprior art even though humidity sensing for such control has been tried.The difiiculty arises in the fact that a domestic clothes dryer isconstantly confronted with loads of different size, different initialmoisture content and difierent bulk. For instance, a clothes dryer mayhave placed therein a light or minimum load consisting of a few shirtsor handkerchiefs. Since constant air fiow with constant heat input isutilized in current domestic dryers, an irregular load of this type issubjected to higher air flow and/or higher heat than is desirable forthe moisture in the fabric. Consequently, this air flow will indicate anincorrect condition of dryness. Also, the seams and folded areas of thearticle of clothing dry more slowly than do the single thickness portions. Thus, it should be seen that the dryness of a light load cannotbe accurately sensed by the prior art devices.

Another irregular load for which a domestic dryer is frequently used isa bulky load wherein a densely woven fabric, such as a shag rug, issought to be dried. Here, also, the moisture is given up very quicklyfrom the exposed surfaces of the pile and the dryer air flow indicates adry condition. This sensed dryness, however, is premature in that thedeeper portions of the pile give up moisture much more slowly. The priorart is devoid of systems which solve this problem and provide anaccurate dryness responsive system for such bulky loads. The best thatthe earlier teachings have offered is a dryer which will accommodate anaverage load, but leave the irregular light and bulky loads tohappenstance. Drying is the removal of an evaporable liquid, usuallywater. Artificial drying is accomplished through the medium of hot airso that the evaporation may be produced at the boiling point in asaturated atmosphere, i.e. at a vapor pressure equal to the atmosphericpressure. With regard to the rate of evaporation, the moisture to beremoved from materials exists either as free moisture, which evaporatesin accordance with the normal liquid vapor pressure, or as hygroscopicmoisture, where the normal vapor pressure is reduced by the absorptiveefiect .of the material. The rate of evaporation of free moisturedepends on (1) the vapor pressure of the moisture in the materialcorresponding to its temperature; (2) the vapor pressure of the moisturein the air corresponding .to its absolute humidity or dew-pointtemperature; and (3) the effective velocity of air over the materialsurface. For a given condition of atmosphere or air movement, the rateof evaporation is proportional to the dif- .-ference in vapor pressurebetween the liquid and the vapor of that liquid in the immediatevicinity. This law holds for any temperature of liquid above thedew-point of the surrounding air irrespective of the dry bulbtemperature of the air.

In drying clothes it is desirable to remove only the free moisture fromthe clothing. If the drying cycle is terminated after this is done, theclothes are neither over- 3,088,221 Patented May 7., 1963 dried norunder-dried. If, however, the drying process is extended, thehygroscopic moisture will be removed from the fabric as well. The resultof such over-drying gives rise to a fabric which is hard and rough. Thefibers are brittle and the lubricity of the fabric is impaired. In someprior art dryers utilizing a conventional timer only, a rough estimatemay 'be made by the operator of the drying time needed for any givenload. Obviously, there is no assurance that the clothing will thus becorrectly dried. "In other prior art devices, an air stream humiditysensing element is utilized and the cycle terminated when the sensingelement indicates a predetermined condition of dryness. This, too, failsto compensate for loads of different size and type and cannot provide adrying system terminating at the proper point. Since the tumbling drumand other dryer components retain considerable heat when the humiditysensing element terminates the cycle, the clothing continues to dry andan over-drying condition results.

To overcome the above and other disadvantages of the prior art devices,the applicants have devised a drying system which automaticallycompensates for different type loads to reflect the proper rate ofdrying. The system further adds a periodic test period wherein thedryness of the fabric is tested in a reduced air supply for an accurateindication of its dryness condition. 'In this way, the applicantsimproved drying system anticipates the desired end point dryness of thefabric and terminates the drying cycle at this condition.

Accordingly, it is an object of this invention to provide in a dryer areduced air flow preheat operation in advance of a drying cycle.

it is also an object of this invention to provide a control system for aclothes dryer which will assure maximum saturation of the dryer exhaustair.

It is another object of this invention to provide a fabric drying systemwherein high heat is utilized during periods of high moisture content inthe fabric and low heat during periods of low moisture content.

A further object of this invention is the provision of a humiditysensitive proper end point termination control arrangement for a dryingcycle.

A still further object of this invention is the utilization of a testperiod in a clothes drying cycle Where air how is reduced to concentratemoisture, raise relative humidity and increase the accuracy of thehumidity sensing control.

It is also an object of this invention to provide a drying controlsystem wherein -a test or time delay period is incorporated to sense thedrop in relative humidity in a given time to insure proper drying ofboth regular and irregular loads.

It is also an object of this invention to make the above test periodautomatically variable in accordance with the type of load to be dried.

Another object of this invention embodies the provision for reducingwattage input to the dryer during final stages of drying to tailor theheat input to the rate at which the clothing being dried can give up itsmoisture.

A more general object of this invention is to provide in a clothes dryera termination control which will distinguish between different types ofloads to insure proper dryer termination for each type load.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein preferred embodiments of the present invention areclearly shown.

In the drawings:

FIGURE 1 is a schematic pictorial representation of this invention;

FIGURE 2 is a sectional view of the timer of this invention;

FIGURE 3 is a sectional view taken along line 3-3 in FIGURE 2;

FIGURE 4 is a sectional view of the timer of this invention taken alongline 1-4 in FIGURE 2;

FIGURE 5 is a fragmentary sectional view taken along line 55 in FIGURE 2showing the speed changing mechanism of this timer in its normal or slowspeed position; 7

FIGURE 6 is a fragmentary sectional view taken along line 55 in FIGURE 2showing the timer speed changing mechanism in its test period or fastspeed position;

FIGURE 7 is an elevational view of the timer speed changing mechanismand block-out pawl to show their operative relationship; and

FIGURE 8 is a graphic representation of a drying cycle for a regular oran irregular drying load.

With reference to FIGURE 1, the control system of this invention issuitable for use with a dryer 10 which encloses a rotatably mountedtumbler drum 12. The dryer 10 is housed in a cabinet 14 having a frontloading access door 16, an air inlet 18 and an air outlet or discharge20. Connecting the inlet 18, the tumbling drum 12 and the discharge orexhaust 20 in series flow relationship is a duct or air passage means22. Disposed also in this series flow relationship is a heater 24 whichmay be energized "for either 118 volts or 236 volt operation. The airflow system of the dryer 10 is motivated by a blower or fan 26 poweredby a motor or prime mover 28 which serves also to rotate the tumblingdrum 12. The components of the dryer 10 described hereinabove areconsidered conventional and should not be construed as limitations onthe application of the drying system to be described hereinafter.

To provide conventional safety features in the clothes dryer 10, a highlimit thermostat 30 may be included to deenergize the heater 24 insituations of undue temperature rise. The normal temperature regulationsfor the tumbling drum 12 is provided by a thermostat 32 which opens andcloses to maintain a predetermined temperature within the tumbling drum.A door switch 34 serves to deenergize the prime mover 28 during periodsin which the access door 16 is opened. When the motor 28 is connected,it should be obvious that both the air flow system and the rotation ofthe tumbling drum 12 will be interrupted as well. Another possiblesafety device is a centrifugally actuated motor switch 36 which closeswhenever motor 28 is in operation as a means for limiting operation ofheater 24 to those times when the blower 26 is operative.

In general, the clothes dryers in the prior art have been terminated atthe end of a predetermined timed cycle or have been terminated by asensed sudden increase in dry bulb temperatures at the exhaust 20. Thisinvention contemplates adding a humidity sensing element 38 which actsto close a switch 40 when the relative humidity of air passing throughthe duct 22 is equal to or below approximately 30% RH. On the otherhand, a differential is included in the operation of the switch 40 sothat the switch is open when the relative humidity is greater than orequal to approximately 40% It should be obvi ous, however, that thedesired differential may be varied in accordance with a particular dryerapplication. The sensing element 38 per se and the means by which itactuates a control switch 40 form no part of this application.

It is not always desirable to have a full air flow through the dryer 10.During Warm-up, it is desirable to utilize the concentrated heat of theheating element 24 to raise cabinet and tumbling drum temperaturequickly. Further, during the drying cycle, the efficiency of the dryer10 is lowered whenever air exhausted through the outlet 20 is not in asaturated condition. That is, if the air passes over the moistenedfabric in the tumbling drum at a faster rate than the moisture can beevaporated from the fabric, the air is discharged in a nonsaturatedcondiapparatus is to be successful.

tion. To provide for preheat, to eliminate discharge of unsaturated airand to aid in providing accurate humidity sensing by the element 39, adamper 42 is pivotally mounted in the duct 22. The damper 42 has anopened first position, as shown in solid line, and a closed secondposition, asshown in dotted line. The damper includes an aperture 44 sothat a limited amount of air may pass through the damper when in itsclosed position. In general, it may be said that the components recitedhereinabove are selectively actuated by a control device or timer 220 toaccomplish the various objects of this invention as follows.

The dryer 10 may be utilized to dry different type loads and may beselectively controlled to adapt the dryer for the optimum drying ofthese different type loads. Generally speaking, a dryer is fashionedwith three types of load. A regular load wherein a standard eight ornine pound collection of cotton clothes makes up the load to be dried.This generally consists of shirts, diapers, cotton dresses and dishtowels. The regular load is the one load most frequently placed withinthe dryer and it is to this particular load that the prior art deviceshave been directed. The thinking in the art apparently has been that ifyou satisfactorily dry the clothes load most frequently encountered, thedryer is sufiiciently successful. However, with the increase in man-madefabrics not generally conducive to fiber absorption of moisture-and theuse of the dryer to dry bulky loads of articles-shag rugs or heavy bathtowels-there arises a sizeable number of loads which we shall callirregular hereinafter. These so called irregular loads must be properlydried also if the One type of irregular load is a light or small loadwherein several shirts and handkerchiefs are thrown into the tumblingdrum 12 to be quickly dried. Where the capacity of the dryer socompletely exceeds the requirements of the job, the prior art has beenunable to successfully control the dryer operation to meet this reducedload. Consequently, if a dryness sensing device was used, it sensedmerely a permature condition of dryness. The reason is simply that thelarge surface area of an article of clothing, such as a shirt orhandkerchief, will quickly give up its moisture; and the air passingthereover will falsely indicate a dry condition. However, the folds ofthe fabric being more dense still retain a quantity of moisture whichmust be removed before the article is truly dry. The characteristics ofthis type of light load also applies to the man-made fabrics wherein asingle ply of fabric evaporates its surface moisture very quickly. Hereagain, the folds retain substantial moisture and, thus, limit theaccuracy of any device sensing the dryness condition of dryer exhaustair.

Another type of irregular load is the bulky or dense load whereinarticles, such as a shag rug, are sought to be dried. Here, a fabricsuch as cotton may be woven into a deep pile. During the course of adrying cycle, the

tumbling drum 12 will be rotated and the heated air 'quired torepeatedly program the dryer for additional drying.

Another way of setting forth the different load situations confronting adomestic dryer is to define the loads as to their rate of moisturewithdrawal. In the normal or regular load, the heat input to thetumbling drum or to the dryer is balanced to the maximum rate ofmoisture withdrawal and the fabric making up this load dries uniformly.In the irregular load, however, the rate of drying is non-uniform. Wherelight loads are involved, the

mass of the article dries more quickly than the folds. In the bulky ordense loads the surface of the fabric dries more quickly than do thedeeper portions of the pile. It is to these varying load situations andvarying rates of drying that the control system of this invention isdirected. Further, the system provides for a minimum waste of heat byinsuring that all air exhausted from the dryer 10 is saturated. Toaccomplish these ends, the timer system described next following isadapted.

Referring again to FIGURE 1, the timer 220 is shown in schematicfashion. Included is a synchronous timer motor 50 driving a shaft 52 ata uniform speed. Connected to the drive shaft 52 is a speed changingmechanism 54 having an adjustable gear train (explained more fullyhereinafter in connection with FIGURES and 6) which may be set to rotatea timer shaft 56 at a fast or test period speed or at a normal slowspeed. This speed changer or transmission 54 also includes a neutralposition for the gear train wherein the timer shaft 52 is disconnectedfrom the timer shaft 56.

The particular automatic drying cycle of this invention is controlled bythree cams carried on the timer shaft 56. An energization and dryingcycle control cam 58 is fixed to shaft 56 and is effective to initiate adrying cycle when a cam surface 60 forces a power supply switch blade 62and a contact 64 into engagement with a contact 66 on a drum drive motorand timer motor switch blade 68 and, sequentially, into a contact 70 ona heater and termination control switch blade '72. The cam 58 has aprimary peripheral surface 74 which engages a follower 61 on the switchblade 62 throughout the drying cycle. Another stepped down cam portion 76 is included during the final portion of the drying cycle so that theheaters are positively deenergized for approximately ten minutes at theconclusion of the drying cycle. This period is devoted to a no-heattumbling operation wherein the clothes are cooled to room temperature.The drying cycle is terminated when the follower 61 drops into adeenergized cam portion 78.

The timer shaft 56 has fixed thereto a second or minimum drying time orblock-out cam 80. A first raised peripheral portion 82 is effective tooverride a premature sensing of dryness by the element 38. Thissituation occurs in the beginning of the drying cycle just after thecycle is initiated. At this point, the heaters 24 have not beenenergized sufficiently long to raise the clothing tem perature to thepoint where moisture will be given up. Thus, the air flowing through theduct 22 to the discharge 20 will indicate a dry condition and thesensing element 33 will prematurely attempt to terminate the dryingcycle. To prevent such a premature sensing, a lockout pawl or follower84 rides on the cam surface 82 for an initial period (approximately tenminutes) of the drying cycle while the relative humidity is building upand the dryer is preheating. Once the terminal point 86 of the camsurface 82 passes the pawl 34, the sensing element 38 is effective toset one of several test sensing periods on a third or test sensingperiod cam 88, as will be described more fully hereinafter.

Another functional surface of the block-out cam 80 is the lock reset camsurface 90, which engages pawl 84 prior to the initiation of each newdrying cycle to force the pawl 84 downwardly against the upward bias ofa spring 92. This prepares the timer for the preheat portion of thefollowing cycle to prevent premature dryer termination, as justexplained.

Lastly, the block-out cam 80 carries a four-minute con tact plate 94which prescribes a minimum test sensing period on the test sensing cam88, should none of the several test sensing periods be automaticallyselected. The contact plate 94 operates in conjunction with contacts 96and 98 to complete a circuit to a test sensing period solenoid shownschematically at 104).

Most significant to the sensing period concept of this invention is thefunctioning of the test period cam 88 which is relatively rotatablymounted on the timer shaft 56 on a sleeve bearing 102. The cam 88 iscomprised of a stop portion 104 and a serrated variable test periodportion 106. For purposes of explanation, the serrated portion 166 canbe considered as having a four-minute test period notch 108 at one endof its arcuate length and a twelve-minute test period notch 110 at theother end. In graduated steps between notches 108 and 110 are aplurality of similar notches which predetermine the duration of selectedtest periods between four minutes and twelve minutes. As aforesaid, thecam 88 is mounted relatively rotatably to the timer shaft 56 and willnormally rotate with the shaft 56 due to a spring 112 wrapped around theshaft and connected at one end to a stud or rivet 113 on the cam 88 andat its other end to a cam stop member 114 which is fixed to theenergization cam 58.

The function of the test sensing period cam 88 depends on the operationof a second pawl member 116 which is interconnected by a connectingpiece or pawl carrier segment 122 with the first lock-out pawl member 84and movable therewith. Restraining both pawls 84 and 116 is a dog lockportion 118 which actuates to release the pawl connector 122 in responseto the energization of the solenoid 10th. The dog lock 118 may have aspring biased normal position overlying the pawl connector 122. This doglock 118 may include schematically a cam surface 129 for resetting thepawls 116 and 84 beneath the dog lock 118 at the beginning of eachdrying cycle. It should be obvious that the pawls 84- and 116 moveupwardly in response to the upward biasing effect of spring 92 if thedog lock 118 is removed from on top of the pawl connecting portion 122and the blockout cam portion 82 is not engaged with pawl 84. Conversely,the timer is reset merely by rotating a users knob 132 clockwise. Withthis movement shaft 56 and cam 80 will be rotated until the lock resetcam surface forces the pawl 84 downwardly.

Pawl 116 and pawl connector 122 will follow, camming the dog lock 118leftwardly until it again returns to overlying locking engagement withthe pawl connector 122.

In accordance with conventional practice, a three-wire residential powersupply 126 may be utilized wherein a power supply line L2 is connectedto a contact 128 which is movable axially with the timer shaft 56.Cooperat ng with the contact 128 is a contact 130 which is engaged whenthe users knob 132 is pressed inwardly by an operator to initiate thedrying cycle. This push-pull on-off switch is of conventional design.

After the knob 132 is pressed inwardly and rotated to the startposition, the timing cycle is energized as follows. Power flows from L2through the on-ofi contacts 128 and 130, the line 134, switch blade 62,contact 64, contact '66, timer motor switch blade 68, lines 135, 136,and the timer motor 50 to ground. With the energization of the timermotor 50, the motor shaft 52 will be rotated to drive a speed changingmechanism in the transmission 54. The structural details of thistransmission will be described more fully hereinafter. Suffice it forthe purposes of schematic representation to say that the transmission 54has a speed changing lever or gear shift 138 which in a raised position139, predetermines a slow or normal speed rotation for the timer shaft56. At this point, it is also important to emphasize that the gear shiftlever 138 is interconnected with the pawls 84 and 116 and is alsoactuated by the movement of solenoid 100. That is, with the dog lock 118in blocking engagement with the pawl carrier segment or connector 122,the clutch 138 is retained in the slow speed position 139, as shownstructurally in FIGURE 5, to be described hereinafter. The gear shift138 also has a fast position, shown structurally in FIGURE 6 andschematically at 140. Intermediate the slow speed gear situation 139(detailed in FIGURE 5) and the fast speed situation of 140 (detailed inFIGURE 6), there is an intermediate or neutral position 142 wherein themotor drive shaft 52 is disengaged from the timer shaft 56.

General Timer Operation At the beginning of a drying cycle (during dryerpreheat and primary moisture evaporation) the timer shaft 56 is rotatedat a slow speed with the speed changing mechanism or gear shift lever138 in the gear situation of 139 (detailed in FIGURE This situation willcontinue for the first phase of the drying operation and prior to thetime that the sensing element first senses a dry condition. After thisfirst sensation of dryness, the speed changing lever 138 of transmission54 is conditioned for the fast speed position 140 and/or the neutralposition 7 142. Only during the cooling ofi period of the drying cyclewill the speed changing mechanism 54 return to its slow speed operation,i.e. during the test sensing periods prescribed by the said firstsensation of dryness and utilized thereafter by this invention, thetimer motor 50 will be driving the timer shaft 56 at fast speed in aclockwise direction, or it will be disengaged therefrom to permit theshaft 56 a spring-biased counterclockwise return when the speed changingmechanism 54 has its gear shift lever 138 in the neutral position 142.

Preheat Operation-Regular Load With the manual rotation of the knob 132to initiate a drying cycle, the follower 61 of the switch blade 62 willberaised by the cam surface 60 to a position on the cam a Thisenergization will start the rotation of tumbling drum 12 and will drivethe fan 26 recreate a circulation of air through the tumbling drum andthe exhaust duct 22. Simultaneously, and from the switch blade contacts64, 66 and '70, the heater 24 will be energized from line 148, the highlimit safety thermostat 30, the temperature regulating thermostat 32,the heater 24, line 150, relay switch blade 152 of relay 151, thecentrifugal motor switch 36 to the other side of the line L1. Thisplaces the heater 24 across 236 volts. The above energized circuitpresents an instantaneous situation since the sensing element 38 and,more particularly, the sensing element switch 40, is placed in thecircuit with the control solenoid 100 from the main switch bladecontacts 64, 66 and 70, through line 148, line 154, the sensing elementswitch blade 40, line 156, line 158, and the solenoid 100 to ground. Thefirst rush of air through the duct 22 is below approximately 30%relative humidity and the sensing element 38 momentarily senses a drycondition to close the switch 40. This closing of switch 40 serves toenergize the solenoid 100 which simultaneously closes the damper 42,opens the relay switch 152 and closes the relay switch 153 and removesthe dog lock 118 from blocking engagement with the pawl and speedchanging carrier 122; However, during this initial phase of the dryingcycle, the pawl 84 bears against the block-out portion 82 of the cam 80and, thus, the removal of the dog lock 118 is ineffective. That is, thetimer motor 50 continues to drive the shaft 56 at its normal slow speedand the pawls 84 and 116 are unable to move upwardly in response to thespring 92. As aforesaid, the interconnection between the gear shiftlever 138 and the pawl carrier 122 prevents the movement of the lever138 to its fast speed or neutral position. The reversal of switches 152and 153 serves to connect the heater 24 across 118 volts instead of the236 volts and, thus, the heater is energized from the switch bladecontacts 64, 66, 70, through line 148, high limit switch 30, thermostat32, one half of heater 24, line 160, relay switch blade 153 to ground.This energizes the heater 24 for low heat at the beginning of the dryingcycle; It should again be emphasized that this is a situation of rathershort duration which conditions the dryer for low heat and reduces airflow immediately after 'energization of the dryer to start a dryingcycle. The rapid preheat occurring during vtive humidity curve has notseated in one of the the plate 94 wipes the contacts .118 prevents thelifting of the pawl reduced air flow stimulates the dryerto commencedrying faster and more efliciently.

Normal Drying Operation-"Regular" Load Referring to both FIGURES l and8, we will assume a regular load of laundry has been placed in thetumbling drum 12 to be dried. The graph in FIGURE 8 charts relativehumidityas the ordinate against time as the abscissa. The drying curvefollowed by the regular load is shown as a dashed line. Thus, we see thedrying cycle initiated in the neighborhood of 30% R.H. As aforesaid,instantaneously the solenoid 100 is energized, the damper 42 closed, andthe heater 24 energized for low heat on 118 volts at approximately 1600watts. The small aperture 44 in the damper 42 permits a reduced flow ofair through the tumbling drum 12 and, thus, allows for a rapid preheatof the dryer structure and the wet clothing within the tumbling drum 12.This reduced air flow also prevents wasting heat by exhausting heatedair from the exhaust opening 20 which has not been saturated byevaporated moisture from the still unheated wet regular load. Again,referring to the graph of FIG. -8, the relative humidity of the air flowpassing the sensing element 38 is shown to increase rapidly from 30% toapproximately R.H. in the first few minutes of dryer operation. (Betweenapproximately 30% and 70% RH. the dashed line curve follows the samepath as the solid line curve.) Although the damper was closed and theheat reduced instantaneously at the beginning of the cycle, the sensingelement 38 soon senses the increased relative humidity and at the point164 on the graph has indicated an exhaust air relative humidity ofapproximately 40% which is sufi'icient to deenergize the solenoid and,thus close the relay switch blade 152 to establish a 236- voltconnection for the full heater 24 and high heat of 4400 watts, as wellas opening the damper 42 for full air flow through the tumbling drum 12.This then establishes bling drum. During this normal period, therelative humidity curve of the exhaust air will rise until it reachesapproximately 90%, at which point, a steady state drying conditionoccurs. This state will remain for a period of time until the bulk ofthe free moisture is removed from the clothing and the curve starts adescending relaportion 166. During this normal high air flow, high heatdrying portion of the curve, the humidity sensing element 38 hasmaintained the switch 40 in an open condition and the solenoid 100 hasbeen deenergized.

However, as the relative humidity of the drying regular clothes loadreaches approximately 30% at control point 168 on the curve, thehumidity sensing element 38 will close the switch 40 and the solenoid100 will be energized 'to close the damper 42, switch the heater 24 forlow heat and select the test sensing period adaptable to the type loadbeing dried.

The timer of this invention includes another feature which effects aminimum four-minute test period should the notches 106 rotate completelypast the pawl 116 before the first control point such as 168 is reached.Such an occurrence is more likely to occur with the ,regular" load inwhich case the control point for energizing the solenoid 100 is reachedafter a period in excess of the approximate IO-minute block-outarrangement by the portion 82 of cam 80. For this purpose, the block-outcam 80 includes a four-minute contact plate 94 which Will engage andconnect the contacts 96, 98 if the pawl 116 notches 106 by the time that96, 98. Note that the plate 94 is aligned with the contacts 96, 98 inthe situation depicted in FIGURE 1 only, i.e. when the dog lock carrier122. Once the solenoid 100 is energized at a control point after theminimum time block-out period controlled by cam portion 82, the entirepawl carrier 122 will raise and the contacts 96,

98, which are integral therewith, will be moved radially inwardly fromthe rotating path of the plate 94. This, of course, will negate thefunction of contacts 96, 98 and the test period will be predetermined ina natural manner with the pawl 116 in one of the best period notches 106most indicative of the load being dried, and best suited to sense thedryness of the load.

Determination of Test Sensing Period-Regular Load As the solenoid 100 isenergized, the dog lock 118 will be withdrawn from overlying the pawlcarrier 112 and the pawls 84 and 116 will be free to move upwardly inresponse to the spring 92. Assuming a minimum time of about ten minuteshas elapsed during the normal course of drying, the block-out portion 82of cam 80 has moved out of blocking engagement with the pawl 84 and thepawl 116 moves upwardly to engage one of the notches 106. The speed withwhich the drying operation reaches the first solenoid energization(graph point 168) after the minimum time prescribed by the block-outportion 82 determines which of the notches 106 into which the pawl 116will fall. The notch selected is indicative of the type load being driedand prescribed the duration of each successive test period. In the caseof a regular load with approximately a normal amount of water retention(say eight-pound load with eight pounds of water), the cam 88 will haverotated with shaft 56 so that the pawl 116 overlies approximately thefour-minute test period notch 108. At the instant solenoid 101] isenergized, pawl 116 moves into the notch 108 and the cam 88 is locked inposition. The timer shaft 56, together with the cams 58 and 80, willrotate relatively to the cam 88 during the balance of the drying cycleuntil the lock reset cam surface 9t? of cam 8t! releases pawl 116 fromthe selected notch or cam '88. Such release will occur only if thesensing element 38 does not register an exhaust air relative humiditygreater than 40% during test period selected four minutes in case of thehypothetical regular load just mentioned. As referred to hereinbefore,the initial upward or locking movement of the pawl 116 also shifts thelever 138 of the speed changing mechanism to its fast position 140 andsets up a locking arrangement whereby the gear shift lever 138 may notagain return to its slow speed position 139. On the graph in FIGURE 8,this situation is reached at the point 168 when the successive testperiod portion of the cycle is initiated.

Test Period Operation-Regular Load During the test period which is shownsubstantially etween the 30% and 40% relative humidity lines on thegraph, the air flow and the heat are reduced. In view of the heatbuildup in the tumbling drum 12, the relative humidity of the reducedc.f.m. exhaust air will start to increase along that portion 170 of thecurve (FIGURE 8). If the regular load is not quite dry, the relativehumidity will again increase to the actuating point of approximately 40%wherein the humidity sensing element 38 will cause the switch 40 toopen, which will, in turn, deenergize the solenoid 100 and return thedryer 10 to full air flow with high heat. It should be recognized atthis point that the drying load is approaching the proper dryness endpoint and the relative humidity will again start to fall along thatportion of the curve 172. As the 30% RH. point is reached, the switch 40will again close to indicate the lower limits of the test period and lowheat low air flow will be reestablished. Again, the relative humiditywill or may start to increase along the curve portion 174. But in thisinstance, there is not suflicient moisture left in the clothes under alow heat low air flow condition to attain the actuating point for thesolenoid and relative humidity will reverse Within the test period andstart falling along a curve 176 and the drying cycle will be terminatedafter the no-heat segment 76 of the cam 58 passes the follower 61.During the test period, the functioning of the timer motor 50, the speedchanging mechanism 54, the cams 5S and 88, are as follows.

As aforesaid, the cam 88 is locked against further rotation at thebeginning of the first test sensing period (point 168 in FIGURE 8). Thisis accomplished when the pawl 116 moves into a notch 106 in accordancewith the time that it takes for the exhaust air relative humidity toreach approximately 30% RH. after the minimum initial time periodcontrolled by block-out cam surface 82. This has been found to give anindication of the type load being driedregular or irregular. Where themoisture is given up uniformly throughout the entire load, the load istermed regular and, generally, a short or four-minute test period willsuffice. To put it another way, a regular load approaches the proper endpoint dryness with a uniform rate of drying or moisture evaporation.Thus, a short test period is sufficient to indicate whether the load istruly dry. On the other hand, an irregular load does not have an evenrate of drying and, thus, a longer test period with the pawl 116 in oneof the notches 106 closer to the twelve-minute test period 110 is founddesirable to insure a complete and proper drying end point for theirregular load. This irregular load will be described next following,but for the purposes of either a regular or irregular load, the drivemechanism will work as follows (see FIGURE 1). When the pawl 116 locksinto a notch such as 168 in cam 88, a gear shift lever 138 will assume aposition 144} and in accordance with an altered gear train in the speedchanger 54, the shaft 56 will be rotated at a fast speed. This moves cam58 and the cam stop 114 affixed thereto in a rotating movement, as shownby the arrow on cam 58. If the cam 58 reaches a point on the peripheryof the drying cycle portion 74, the successive test periods willterminate and a no-heat cycle along cam surface 76 will be initiatedjust prior to the end of the drying cycle. Note that the stop portion194 of test period cam 88 is located relative to drying cycle cam 58 andcam stop 114 in accordance with the particular notch 106 in which thepawl 116 is locked. This prescribes the test period duration since theamount of the peripheral edge 74 of the cycle cam 58 on which thefollower 61 can operate is thus limited.

In a normal or regular load, cam 58 and, thus, cam stop 114 may rotateor oscillate back and forth several times limited in one direction bythe point 180 of cam 58 and by the stop 104 of cam 88. Thus, the limitsof the test period are defined. If the solenoid 100 is again deenergizedto indicate the clothing is not quite dry before the point 180 of cam 58is reached, the gear shift 138 will assume the neutral position 142, thedrive shaft 52 will be disengaged from the timer shaft 56 and the spring112 will force the cam 58 to rotate counterclockwise until the stop 114strikes the cam protuberance 104. This may be repeated several timesuntil the relative humidity of the exhaust air fails to rise to theapproximately 40% RH. level prior to the time that the cam 58 reachespoint 180, i.e. the end of the last test sensing period. In the lasttest sensing period also (curve portion 174 in FIG- URE 8) the solenoid109 remains energized to close the damper 42 and condition the heater 24for 118 volt low heat operation. As the follower 61 of the power supplyswitch blade 62 reaches the no-heat start point 180 on cam 58, power tothe heater 24 and to the humidity sensing control system will beinterrupted. Substantially, simultaneously the lock reset portion 96* ofcam 80 will force the pawl carrier 1-22 downwardly and reconnect thetimer motor driving shaft 52 to the timer shaft 56 for normal slow speedtiming operation. Thus conditioned the timer cam 58 will program ano-heat portion of the drying cycle for approximately 10 minutes duringwhich time the clothes are cooled to handling temperature. The dryingcycle terminates when the follower 61 drops into cam portion 7 8,thereby deenergizing the entire dryer. In this way, the regular clothesload is properly dried 'user knob 132.

Preheat Operatinlrregular Load I With reference now to FIGURE '8 and,more particularly, the solid line graph thereon, the explanation of thedrying cycle for such items as a shag rug will be clearly set forth.Atthe beginning of the drying cycle, the relative humidity of aircirculating through the tumbling drum will be at room conditions.Similarly, the temperature of the dryer components will be approximatelyroom temperature and the fabric placed within the tumbling drum will beapproximately at that temperature at which the washing operation wasterminated, assuming, of course, that the drying operation immediatelyfollows the washing cycle. It is one of the objects of this invention toprevent wasting heat during the initial portion of the drying cycle.Since neither the shag rug nor the dryer components are up to dryingtemperatures, it is desirable to retain as much heat within the dryer 18until such drying temperatures are reached. The humidity sensing element38 maintains the switch 40 closed when the relative humidity of theexhaust air is somewhere below 30%. .It is believed that exhaust airwith a relative humidity below thisfigure is substantially dry and notserving any drying purpose. As the cycle is initiated, the controlsolenoids 180 will be immediately energized from L2, contacts 128, 130,line 134, the power supply switch blade 62, contacts 64, 66 and 70,heater and control system switch blade 72, line 148, line 154, humiditysensing switch 40, line 156, line 158, solenoid 100 to ground. Theenergization of the solenoid 100 will reverse the switches of relay 151closing the low heat relay switch 153 and opening the high heat relayswitch 152. Simultaneously, the damper 142 will be moved to its dashedline closed position and the air flow through the tumbling drum reducedin accordance with the size of an aperture 44 in the damper 42. Thisaperture may be approximately one inch in diameter to allow a minimumair flow to pass the'sensing element 38. With the heater 24 thusenergized, the temperatures within the dryer cabinet 14 will immediatelyrise. Prime mover or motor 28 is energized at this time from L2,contacts 128, 138, line 134, power supply switch blade 62, contacts '64,66, drive motor switch blade 68, line 135, line 144, the door switch 34and the motor 28 to ground. With the energization of motor 28, theblower 26 will be energized to induce a flow of air through the tumblingdrum 12, which is now being rotated by the motor 28. This preheatoperation or period is of rather 'short duration and terminates at point164 on the irregular load graph of FIGURE 8. At this point, which occursat approximately 40% relative humidity for the exhaust air in duct 22,the sensing element switch 40 will be opened to deenergize the solenoid100 and the damper 42 will return to its open position and the relay 151will be repositioned to energize the heater 24 for a high heat or 4400watt input drying operation. This concludes the preheat operation andthe irregular load advances into the normal drying operation.

Normal Drying Operation-Irregular Load During the short preheat periodthe fabric, in this case the shag rug, and the dryer components arebrought up high heat high air flow drying is in line with the concept ofthis invention to insure maximum moisture content for any air exhaustedfrom the dryer '10. Up to the point 164, no conclusion has been made bythe timer of this invention to determine the type of load in thetumbling drum .12. During the preheat operation the solenoid 100 wasenergized to close the damper 42 and adjust the heaters .for low heatl600-watt operation. It will be noted on the schematic showing of FIGURE1 that the energization of solenoid .100 will also remove a dog lock 118from blocking engagement with a pawl carrier 122. But during thisinitial stage of the drying operation, we have not reached a stabledrying condition and the type load cannot yet be accurately sensed. Forthis reason, an enlarged or block-out portion 82 is formed on theminimum test period or block-out cam to prevent the pawl 84 from movingupwardly. The pawl 116, being integrally formed with the pawl 84, alsocannot move and the removal of the dog lock 118 during this initialdrying phase is ineffectual to release the pawl carrier. Normally, also,the energization of solenoid serves to shift the clutch lever 138 in thespeed changingmechanism 54. Even though it is not so shown in FIGURE 1,the gear shift lever 138 is interconnected with the pawl carrier 122 andis, thus, prevented from being shifted by the energization of thesolenoid 100 during the preheat operation.

As cited immediately above, the normal portion of midity of the airexhausted will increase rapidly during this early portion 200 of thedrying cycle. Due to the .bulk or dense construction of a heaving rug,the surface 'area thereof is comparatively small to the mass of the rug;Therefore, the air passing over the tumbling rug will quickly dry thissurface and the relative humidity of the exhaust air will soon startdecreasing along the irregular curve falling rate portion 202, therebygiving erroneously a sensation of dryness for the shag rug.

Determination of Test Sensing Periodlrregular Load It will be noted thatthis fallacions sensing of dryness in the dense shag rug comes earlierthan the falling rate portion 166 of the regular load curve. Obviously,the humidity condition of the circulating air is not truly appraisingthe dryness of the bulky or shag rug load. Deep within the pile of therug, most of the moisture still remains. However, this early fallingrate curve is an indication of the type load being dried. Where suchload happens to be a light load of man-made fabrics, the largest surfaceof such fabrics, will dry quickly, whereas the fold and seams retainmoisture. This may be equated to the bulky or shag rug load wherein thesurface area quickly dried leaving moisture still entrained deep withinthe pile of the article. The recognition of characteristics of irregularvs. regular loads in a drying cycle has led to one of the major conceptsof this invention a timer'which can sense the type load being dried andthen automatically make compensating adjustments to adapt a test sensingperiod to the particular drying load.

Mechanically and with reference to FIGURES 1 and 8, this is accomplishedas follows for the hypothetical shag rug load. As the condition ofexhaust air bypassing the sensing element 38 reaches a control pointcondition 204,

.the sensing element 38 reacts to close the switch 40. This spring 92.Depending on the length of time that has elapsed prior to reaching thecontrol point condition 204, the pawl 116 will snap into one of thenotches 106 of the rotating cam 88. As best seen in the graph of FIG-URE 8, it takes less time for the irregular load to reach its controlpoint 204 than it does for the regular load to reach control point 168.Thus, it is proper to assume that the pawl 116 will fall into one of thenotches 106 nearer to the twelve-minute test period notch 110. -With theupward movement of the pawl carrier 122 and the continued energizationof the solenoid 100, the clutch lever 138 will be held in a fast speedposition 140 and the dryer will be conditioned for a test periodoperation suitable for use with the particular fabric load being dried.

Test Period Operationlrregular Load Immediately after the control point204 has been reached and the solenoid 100 energized, the test periodoperation of the instant drying cycle commences. These test periods willcontinue consecutively until the sensing element 38 fails to register anincrease in exhaust air relative humidity during one of the testperiods. At this point, the drying cycle will move into a no-heatoperation prior to cycle termination.

In operation, the test period works as follows. As the condition of theexhaust air in duct 22 reaches the approximate 30% R. H. level (controlpoint 204 of the graph), the sensing element switch 40 will close toenergize the solenoid 100. The damper 42 will be closed and the heater24 switched for low heat operation with switch 153 being closed and 152opened. A reduced c.f.m. low heat air flow will, thus, be establishedwith a minimum sensing quantity of air allowed to pass through theaperture 44 in the damper 42. This restricted air flow overcomes thefallacious indication of dryness evidenced by the rapidly falling ratecurve portion 202. Since the shag rug is not truly dry and the moisturewithin the dense pile continues to be given off, the reduced air flowwill increase in relative humidity and the drying curve will againincrease along a curve portion 206. Simultaneously with the closing ofthe damper and the low heat adjustment for heater 24, the solenoid 100serves to pull a gear shift lever 138 to establish a fast speed drivingrelationship between the timer motor 50 and the timer shaft 56. Themechanical structure of this gear shift mechanism will be set forthhereinafter in connection with FIGURES 6 and 7. Sufiice it to say thatafter the first test period is established at control point 204, theshaft 56 will be ro tated at fast speed along the curve portion 260 andwill be disconnected from timer motor 50 along the curve portion 208 sothat the next following test period may be reestablished. schematically,this is accomplished when the upward movement of pawl 116 locks the cam88 against rotation. Since earns 53 and 80 are afiixed or keyed to theshaft 56, they will continue to rotate with shaft 56 at the fast speedprogrammed into the speed changing mechanism 54. As cam 58 rotates withthe power supply follower 61 on cam portion 74, the integral cam stop114 will be rotated as well. The spring 112, being connected both to thepawl-stopped cam 88 and to the cam stop 114, will wind itself around thecam shaft 56. Should the relative humidity sensed by the element 38 riseto the upper actuating point for switch 40 (equal to or aboveapproximately 40% the switch 40 will open to deenergize the solenoid100. The deenergization of the solenoid will again open the damper 42and adjust the heater 24 for high heat operation. *It will also releasethe clutch lever 138 for return to a neutral position wherein the shaft52 will be disengaged rom shaft 56 and the spring 112 will bias the cam58 in a counterclockwise direction until the cam stop 114 engages theraised portion 104 on the fixed cam 88. At the completion of this springbiased return (along curve portion 208), another test sensing period isready to begin.

During the spring biased return of cam 58 the dryer is again operatingwith high heat and high air flow and tends to entrain moisture from theshag rug faster than the rug can give up such moisture. Thus, again therela tive humidity will fall quickly to the next following control pointlevel, say 209 along the 30% RH. line and the solenoid will be againenergized to initiate the second test sensing period which will beidentical in duration with the first. The test sensing period continueswith the fast driving relationship of cam 58 followed by a neutraldriving relationship in which the cam returns to a test period startposition. Throughout the consecutive test periods, the shag rugcontinues to give up its mois ture from its dense pile. Intermittently,along curve portions 206, the air flow is reduced as is the heat tominimize exhausting unsaturated hot air to the atmosphere. As the testperiods continue, the effect of this invention is to increase theefficiency of the dryer by eliminating the waste of exhausting dry hotair. The system also maintains a close observation on the condition ofthe dense load being dried. This is to assure against overdrying whereinthe fabric can become rough and the fibers brittle. After a period oftime determined by the quantity of materials or rugs in the dryer, thelast control point 210 will be arrived at. Hereto, the solenoid 100 willagain be energized as the humidity sensing switch 40 is closed. The airflow will be again reduced and the heater input decreased from 4400watts to 1600 watts. With the reduced air flow over the rug, there maybe a period along the curve portion 212 wherein the moisture againstarts to cause an increase in exhaust air relative humidity. However,the condition of the rug is so close to its true correct dry point thatthe relative humidity fails to rise to the switch 40 actuating point ofapproximately 40%. Consequently, the relative humidity of the reducedflow exhaust air tops out and starts to fall. It must be remembered thatduring the last test period, the solenoid 100 is continuously energizedand the cam 53 is being rotated at a fast speed. If the follower 61 ofthe power supply switch blade 62 reaches the drop off point on theperiphery of cam 58, the power supply will be broken between contacts 66and 70 to deenergize the heater 24 and the humidity control system,thereby restoring full air flow. A no-heat portion of the cycle is,thus, initiated along the cam portion 76.

N0 Heat Operation-Irregular Load With the switch blade follower 61 onthe no-heat cam portion 76, power is still directed to the drive motor28 and the timer motor 50 through the contacts 64, 66. During the testsensing period, as related herein above, the shaft 56 has been driven ateither a fast speed in a clockwise direction or is coasting in acounterclockwise position in response to the biasing effect of spring112. During the final test period, as indicated along curve portion 212,for a bulky load, the reset portion 90 of the cam 30 will engage theblock-out pawl 34. Thus, the pawl 84 is cammed downwardly against theupward bias of spring 92 to reset the pawl carrier 122 in its lowerposition. Since the gear shift lever 138' is integrally associated withthe pawl carrier 122, the speed changing mechanism 54 will be reset to aslow driving relationship, as seen structurally in FIGURE 5. Once thelock reset point 90 engages the pawl 84 to reestablish the slow drivingrelationship of shaft 56, the test period is complete. Following this,the timer will move through a prescribed noheat course along the camportion 76 until the follower 61 drops into the cam portion 78, shown inFIGURE With this action, power to the dryer motors 28 and 50 and to thetimer control system is deenergized and the drying cycle completed.

The control system of this invention is designed to end the drying cyclewhile the material being dried retains a little moisture. It is knownthat relative humidity is a function of temperature as well as moisture.Thus, the clothes drying cycle is terminated with the fabric at a 15slightly elevated temperature. This temperature will drop as the fabricreaches room temperature and the retained moisture will aid in givingthe fabric the same relative humidity as its surrounding atmosphere.Another factor which must be consideretd is that the sensing element 38is sensing a relative humidity of the circulating air and not the fabricitself. The slight retention of moisture in the fabric at the conclusionof this drying cycle will not be noticed when the fabric reaches anequilibrium condition with the surrounding atmosphere, i.e., therelative humidity or hygroscopic moisture retention of the fabricassumes a correct figure when the fabric is cooled. The fibers areneither brittle nor is the fabric rough when the proper dryingtermination occurs. Only the free moisture .is removed from the fabricand the hygroscopic moisture is retained. This is accomplished throughthe use of a test period technique, the duration of which is adapted toa particular clothes load and the repetitive nature of which serves tobracket in on the proper end point dryer termination.

The explanation set forth in connection with the regular load and theirregular load is believed to adequately define the concept of thisinvention to allow any one skilled in the art to design a timer inaccordance with these inventive precepts. For purposes of clarity, andwith reference to FIGURE 2, the applicants have embodied this designinto a timer 220, wherein equivalent par-ts carry identical referencenumerals to those used in 7 connection with FIGURE 1. The timer iscomprised of a body portion 222 having a top wall portion 224, a bottomwall portion 226 and side walls 228 and 230. A

removable front plate 232 is fastened as at 234- to an open ,end 236 ofthe timer body 222. Similarly, a timer motor support plate 238 closes arearward open end 240.

. Centrally located in the timer body 222 is a central partition 242which separates the timer body into a speed changing or transmissionchamber 54 and a cam actuated timing portion 244. A timer shaft 56extends axially through the cam actuated timer chamber or compartment244 and is journaled at 246 in an enlarged bearing portion of thecentral partition 242 and in an opening 248 in the front cover 232. Thetimer shaft 56 is adapted for limited axial movement to open and closethe main line contacts 128 and 130, more clearly seen in FIGURES 3 and4. To mechanically actuate the contact 128 into engagement with thecontact 130, a contact carrier or support (FIGURES 3 and 4) 250 isformed with an actuating arm 252 which is engaged by the rearwardsurface 254 of the cam 80 when the shaft 56 is pushed inwardly. Toprovide for limited axial movement of the timer shaft 56, the shaft isbifurcated at 256 to receive a driving element 258 inserted therein. Inaccordance with conventional practice, the timer shaft 56 may include arod 260 aflixed to the shaft for rotation therewith. A cam portion "262formed on the front cover 232 will serve to cam theshaft 56 in anaxially outward direction during final rotation of the shaft 56. Thisaxially outward movement removes the biasing surface 254 of the cam 80from the contact support plate 250 and the main line contacts 128 and130 are disengaged.

The actuating cams for the timing mechanism of this invention arecarried on the timer shaft 56 and adapted for axial movement therewith.The block-out cam 80 is aflixed to a support sleeve 264 which, in turn,is keyed or fastened in any suitable manner to the timer shaft 56.

The drying cycle cam 58 is loosely fitted over the shaft' 56 but isrestrained against axial movement and extensive rotational movement by acam retention bracket or disc 266. This bracket has several fingerportions 268 WhlCh extend through an oversized opening 270 in the cam258.

On the opposite' side of the cam 58 is another disc-like portion 272having openings into which the finger portions 268 insert. Both thedisc-like portion 272 and the bracket 266are secured to the timer shaft56 and, thus,

limit the axial movement of the cam 58. Further, the

finger portions 268 in extending through the cam apertures 270 limit therelative rotational motion of the cam and provide for snap action of thecontact switch blades 62, 68 and 72. As seen in FIGURE 2, it is possibleto form one of the bracket fingers as at 274 with an extended terminalportion 114 to serve as the cam stop 114 which rests against theenlarged portion 104 of the cam 88.

Interposed between the generally shaft-fixed cams 58 and 80 is the testperiod determining cam 88' which is supported on and fixed to a bearingsleeve 102 relatively rotatably carried on the timer shaft 56. In FIGURE2, it can be seen that raising the pawl 116 into engagement with one ofthe teeth 106 in cam 88 will aflix the cam 88 so that the shaft 56 andthe cams 58 and 80 may continue to rotate relatively to the cam 88.

Reference may now be had to FIGURES 2, 5, 6 and 7 for a more particulardescription of the pawl carrier assembly of FIGURE 7 which provides forthe interaction of pawls 84, 116, four minute minimum test periodcontacts 96, 98 and timer speed charging lever 138. Within the speedchanging compartment 54 a pawl manipulating link 280 is pivotallymounted on a pin 282,

through partition 242, a washer 281 being interposed for ease ofmovement. The link 280 is biased by a spring For interconnecting thepawls 84 and 116 with the pawl manipulating link or lever 280 anaperture 288 is formed in the partition 242. A pin 290 extends throughthe.

aperture 288 and connects to the pawl manipulating link 280 as at 292.Thus, as the link 280 pivots about the point 282, the pin 290 will bemoved up or down in an arcuate path. Rotatably mounted to the pin 290,as at 294, is a pawl lift link 296. This link 296 is fastened to thepawl support or carrier 122 which integrally connects the pawls 84, 116:and the contacts 96, 98 for movement as one unit. With thisrelationship of parts, when the pawl actuating link 280 moves from thespring depressed position of FIGURE 5 to the raised or counterclockwisepivoted position of FIGURE 6, the rod 290, the lift link 296, and, thus,the pawls 84 and i116 raise as well. Of course, the final determiningfactor as to whether the pawls 84 and 116 will raise depends on thefreedom of pawl 84 to move upwardly. This upward movement is madepossible by the removal of the block-out portion 82 of cam 80 frombiasing engagement with the pawl 84. It should now be seen (FIGURE 7)that the carrier 122 will be acted upon by the direct biasing effect ofthe spring 92 and the indirect biasing elfect of spring 284. Thesesprings 92, 284 are effective to lift the pawls 84, 116 if the cam 80 isin the correct relationship to pawl 84. Another factor limiting themovement of the pawl actuating link 280 is a gear carrier support 300which has an exmotor 50 through a motor shaft 52. Permanentlyinterconnected with the gear 302 is a larger driving gear 304 carried ona shaft 306 which is journaled in the removable rear wall 238 and in thecentral partition 2 42. Also carried by the shaft 306 is an elongateddriving gear 308 which rotates at the same speed as does gear 304. Forthe purpose of the two-speed driving arrangement of this invention, thepinion 302 and the driving gears 304 and 308 retain the same drivingrelationship for either slow speed or fast speed.

The two-speed arrangement of this timer is effected by the particularrelationship of a gear carrier support plate 300 which is relativelypivotally mounted at 310 to the driving gear shaft 306. On the carriersupport plate 300 V 17 is arranged a slow speed gear assembly 311 havingan integrally formed large gear portion 312 and a small gear portion313.

The assembly 311 is journalled in an opening 320 in the carrier plate309. At the other side of .the gear carrier plate 30%) is an opening 318which journals a fast speed gear 314.

Reference may now be had to FIGURE 7 for a more particular descriptionof the motion of the gear carrier support plate 330. The carrier plateis formed with an aperture 318 in which the fast speed gear 314 isrotatably mounted and a slow speed aperture 326 in which the slow speedgear assembly 311 is carried. As explained hereinbefore, the plate 300is ported at 310 to pivot about the shaft 366 and is controlled in itspivotal motion by the solenoid operated gear shift lever 138 which ishooked around a turned up portion 322 on the carrier plate 300. Itshould thus be seen that when the solenoid 1% is energized, the gearshift arm 138 will be drawn leftwardly to pivot the gear plate 360 in aclockwise direction. This pivotal movement is against the bias of aspring 321 which is afiixed at 324 to the side wall 228 of the timercasing. Each time that the solenoid 100 is energized, the fast speedgear 314 is pivoted upwardly into driving engagement with a timershaft-aflixed driven gear 332. The timer shaft gear 332 is carried on anaxially fixed shaft portion 334 which is journaled in the partition 336.Although the shaft 334 is not fixed to the timer shaft 56, it willtransmit rotational movement thereto through the integral tongue 258 andbifurcated end 256 of the timer shaft 56. Any suitable locking discarrangement 337 may be utilized to secure the timer shaft gear 332 tothe shaft 334.

To summarize the two speed operation of the timer shaft 56, the timermotor 50 operates to drive a shaft 52 to which the pinion 392 isconnected. The gear 304 is driven from the pinion 302 and transmits thisrotational motion to the gear 3%. Both the slow speed gear 314 and thehigh speed gear 312 are drivingly connected to the gear 393 and bothwill be constantly rotated by gear 308. However, when the solenoid 100is energized, the lever 138 causes the plate 300 to pivot to theposition shown in FIGURE 6 wherein the fast speed gear 314 is engageddirectly with the timer shaft gear 332 and the timer shaft will berotated at fast speed, as during the test sensing periods.

The operation of the solenoid actuated dog lock 118 will now beexplained as it relates to the alternating fast speed gear shiftposition 14% and neutral position 142 (FIGURE 1). Referring to FIGUREfor the timer gear driving situation prior to the energization ofsolenoid 100, the dog 286 of the pawl actuating link 280 is shownbearing against the dog lock portion 118 of the carrier plate 300. Thisprevents the pawls 84 and 116 from lifting, since they areinterconnected with the dog 286 through the links 280, 2&6 and 2%.However, once the solenoid 19!} is energized (relative humidity below30% at sensing element 38), the plate 389 pivots in a clockwisedirection to the arrangement of FIGURE 6 and the dog 286 is biased bythe spring 284 to a position against an edge 340 of the plate 3%. Inthis situation, fast speed is established for the timer shaft 55 and thecams 58 and 80. On the other hand when the solenoid 160 is deenergized(relative humidity above 40% at sensing element 38), the shift lever 138will attempt to move to the slow speed position of FIGURE 5. This,however, is prevented by the engagement of the dog 285 with the stopportion 322 on the carrier plate 300. In this intermediate position,neither gear 314 nor the gear 313 is engaged with the timer shaft gear332. Thus, the timer motor 50 is completely disengaged from the timershaft 56 and the timer shaft is free to move in response to the returnbias of the shaft spring 112. This situation occurs during all but thelast test sensing period, as described hereinabove.

It should now be seen that an improved timer has been provided wherebyautomatic termination of a drying cycle can be accurately accomplished.This timer concept embodies means for eliminating waste of heated airwithout its proper saturation with moisture. It provides further forsensing the type of load being dried and in response thereto prescribinga test period adapted particularly for that load sensed. Still further,it embodies means for utilizing the sensing period programmed tominimize over-drying the load and to insure an accurately dried fabricwhich can then be cooled to room temperature.

While the embodiments of the present invention as herein disclosed,constitute preferred forms, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

1. In combination with a clothes dryer having means for inducing airflow through said clothes, controllable means for heating said air flowwith high and low heat input, means for restricting said air fiow andmeans for sensing the humidity of said air flow on the exhaust side ofsaid clothes, a timer comprising, means for controlling said restrictingmeans to reduce said air flow and for controlling said heating means forlow heat input in response to a predetermined low humidity conditionsensed by said sensing means to concentric humidity, means releasablyassociated with said control means and simultaneously actuatabletherewith for setting a repeatable variable clothes dryness test periodoperable between said predetermined low humidity condition and apredetermined high humidity condition when said control means reducessaid air flow and controls said heating means for low heat input, andmeans for terminating said drying when said sensing means senses a drycondition throughout one of said repeatable test periods.

2. In combination with a dryer having means for inducing air flowthrough said dryer, controllable means for heating said air flow withhigh and low heat input, means for restricting said air flow and meansfor sensing a moisture condition of said air flow on the exhaust side ofsaid dryer, a timer comprising, means for controlling said restrictingmeans to reduce said air flow and for controlling said heating means forlow heat input in response to a predetermined decreased moisturecondition sensed by said sensing means, means actuated by said controlmeans for initiating a variable moisture condition test period operablebetween said predetermined decreased moisture condition and apredetermined increased moisture condition when said control means reduces said air flow and controls said heating means for low heat input,and means for terminating said drying when said sensing means senses acondition of no free moisture throughout said test period.

3. In combination with a dryer having means for inducing a drying airflow through said dryer, means for restricting said air fiow and meansfor sensing a moisture condition of said air flow on the exhaust side ofsaid dryer, a cycle governing device comprising, means for controllingsaid restricting means to reduce said air flow in response to apredetermined first moisture condition sensed by said sensing means,means actuated by said control means for setting the duration of atleast one variable moisture condition test period operable between saidpredetermined first moisture condition and a predetermined secondmoisture condition above said first moisture condition when said controlmeans reduces said air flow, and means for terminating said drying whensaid sensing means fails to sense said predetermined second moisturecondition throughout one of said at least one moisture condition testperiod.

4. In combination with a fabric dryer having means for inducing a dryingair flow through said fabric, means for reducing said air flow and meansfor sensing a moisture condition of said fabric on the exhaust side ofsaid fabric,

19 a timer comprising, means for controlling said reducing means inresponse to predetermined first and second moisture conditions sensed bysaid sensing means respectively to reduce and increase said air flowperiodically before the termination of said drying, means activated bysaid control means for setting a repeatable variable moisture conditiontest period operable between said first and second moisture conditionswhen said control means reduces said air flow, and means for terminatingsaid drying when said sensing means senses a dry condition throughoutone of said repeatable test periods.

5. A clothes drying system comprising, a rotatably mounted container,means for rotating said container, air passage means connected to saidcontainer, means for creating a stream of air in series flowrelationship through said container and said passage means, means forheating said air, means in said passage means having a first positionfor restricting said air and a second position for passing said air,said restricting means having means for passing a limited amount of saidair when said restricting means is in said second position, a humiditysensing element in said air passage means, and a control device forgoverning said drying system, said control device havmg a timer shaft,means for driving said shaft, speed changing means between said shaftand said driving means for rotating said shaft at a fast and slow speedincluding means for disengaging said driving means from said shaft, adrying cycle cam on said shaft for selectively actuating a plurality ofswitches to energize and deenergize circuits associated with saiddriving means, said heating means, said air stream creating means andsaid rotating means, said drying cycle cam having a stop member, avariable clothes dryness sensing period cam relatively rotatably mountedon said shaft and having a stop portion selectively engageable with saidstop member and a serrated test period portion, said serrated portionhaving a plurality of notches, a minimum drying time cam on said shafthaving a block-out portion and a minimum sensing period electricallyconducting contact plate, a follower for said minimum drying time camhaving a first pawl for engaging said block-out portion, a second pawlintegral therewith for engaging one of said plurality of notches and apair of switch contacts in series electrical fiow relationship with oneof said plurality of switches for engaging said contact plate if saidsecond pawl does not engage said one of said notches, a solenoidresponsive to said humidity sensing element or the engagement of saidswitch contacts with said contact plate for controlling said pawls, saidspeed changing means, said heating means and said air restricting means,whereby when said first pawl is out of engagement with said block-outportion, said second pawl engages said one of said notches, said speedchanging rneans is shifted to fast speed and said air restricting meansIS moved to said first position for a clothes dryness sensing period inaccordance with the said one of said notches engaged by said secondpawl.

6. A clothes drying system comprising, a rotatably mounted container,means for rotating said container, air passage means connected to saidcontainer, means for creating a stream of air in series flowrelationship through said container and said passage means, means forheating said air, means in said passage means having a first portion forrestricting said air and a second position for passing said air, saidrestricting means having means for passing a limited amount of said airwhen said restricting means is in said second position, a humiditysensing element in said air passage means, and a control device forgoverning said drying system, said control device having a timer shaft,means for driving said shaft, speed changing means between said shaftand said driving means for rotating said shaft at a fast and slow speedincluding means for disengaging said driving means from said shaft, adrying cycle cam on said shaft for selectively actuating a plurality ofswitches to energize and deenergize circuits associated with saiddriving means, said heating means; said air stream creating means andsaid rotating means, said drying cycle cam having a stop member, avariable clothes dryness sensing period cam relatively rotatably mountedon said shaft and having a stop portion selectively engageable with saidstop member and a serrated test period portion, said serrated portionhaving a plurality of notches, a minimum drying time cam on said shafthaving a block-out portion, a follower for said minimum drying time camhaving a first pawl for engaging said block-out portion and a secondpawl integral therewith for engaging one of said plurality of notches, asolenoid responsive to said humidity sensing element and in serieselectrical flow relationship with one of said plurality of switches forcontrolling said pawls, said speed changing means, said heating meansand said air restricting means, whereby when said first pawl is out ofengagement with said blockout portion, said second pawl engages said oneof said plurality of notches, said speed changing means is shifted tofast speed and said air restricting means is moved to said firstposition for a clothes dryness sensing period in accordance with thesaid one of said notches engaged by said second pawl.

7. A method of controlling a fabric drying cycle by a dryer having meansfor creating an air flow, means for reducing said air flow, means forsensing the dryness of said air and a variable heating means comprisingthe steps of, applying a reduced air flow and reduced heating during afirst portion of said drying cycle, applying an increased air flow andan increased heating during a second portion of said drying cycle,applying a reduced air flow and reduced heating during a third portionof said drying cycle, repeating said third portion of said cycle, andsensing the dryness of said fabric during said third portions of saiddrying cycle wherein said air flow and said heating are reduced untilsaid fabric is dry, said steps of applying and sensing being under thecontrol of said sensing means.

8. A method of controlling a clothes drying cycle by a dryer having anair circulating means, a damper connected to said air circulating meansand a variable heating means comprising the steps of, closing saiddamper and adjusting said heating means to a low heat during a firstportion of said drying cycle, opening said damper and adjusting saidheating means fora high heat during a second portion of said dryingcycle, intermittently closing said damper and intermittentlysimultaneously adjusting said heating means for low heat to initiateeach of a series of third portions of said drying cycle, and sensing thedryness of said clothes during said third portions of said drying cycleuntil said clothes are dry.

9. A method of controlling a fabric drying cycle by a dryer having anair circulating means, means for restricting said air circulating meansand a variable heating means comprising the steps of, energizing saidrestricting means and adjusting said heating means to a low heat duringa first portion of said drying cycle, deenergizing said restrictingmeans and adjusting said heating means for a high heat during a secondportion of said drying cycle, intermittently energizing said restrictingmeans and intermittently simultaneously adjusting said heating means forlow heat to initiate each of a series of third portions of said dryingcycle, and sensing the dryness of said fabric during said third portionsof said drying cycle for controlling said restricting means and saidheating means whereby said restricting means is dryness responsivelyenergized and said heating means is dryness responsively adjusted forlow heat until said fabric is dry.

10. In combination with a dryer having means for producing air flowthrough said dryer, controllable means for heating said air flow, meansfor restricting said air flow and means for sensing a moisture conditionof said air flow on the exhaust side of said dryer, a timer comprising,means for controlling said restricting means to reduce said air flow inresponse to a predetermined descreased moisture condition sensed by saidsensing means, means actuated by said control means for initiating avariable moisture condition test period operable between saidpredetermined decreased moisture condition and a predetermined increasedmoisture condition when said control means reduces said air flow, andmeans for terminating said drying when said sensing means senses acondition of no free moisture throughout said test period.

11. In combination with a dryer having means for producing air flowthrough said dryer, controllable means for heating said air flow withfirst or second heat input, means for restricting said air flow andmeans for sensing a moisture condition of said air flow on the exhaustside of said dryer, a timer comprising, means for controlling saidrestricting means to reduce said air flow and for controlling saidheating means for said first heat input in response to a predetermineddecreased moisture condition sensed by said sensing means, meansactuated by said control means for initiating a variable moisturecondition test period operable between said predetermined decreasedmoisture condition and a predetermined increased moisture condition whensaid control means reduces said air flow and controls said heating meansfor said first heat input, and means for terminating said drying whensaid sensing means senses a condition of 110 free moisture throughoutsaid test period.

12. An arrangement for controlling a dryer in a drying cycle for moistfabric comprising, means for initiating the drying of said moist fabric,means for sensing predetermined first and second moisture conditionsleaving said fabric before said fabric is dry, means actuatable after adelayed interval in response to the sensing of said predetermined firstmoisture condition by said sensing means for selecting a fabric moisturetest period variable in duration in accordance with the time elapsedbetween the initiation of said drying and the sensing of said firstmoisture condition, and means for repeatedly comparing the time periodnecessary to raise the moisture condition leaving said fabric from saidfirst moisture condition to said second moisture condition with saidfabric moisture test period until said fabric is dry.

13. An arrangement for controlling a dryer having means for producing anair flow and means for changing said air flow in a drying cycle formoist fabric comprising, means for initiating the drying of said moistfabric in said air flow, means for sensing predetermined first andsecond moisture conditions in said air flow downstream from said fabricbefore said fabric is dry, means actuatable after a delayed interval inresponse to the sensing of said predetermined first moisture conditionby said sensing means for selecting a fabric moisture test periodvariable in duration in accordance with the Hme elapsed between theinitiation of said drying and the sensing of said first moisturecondition, and means for repeatedly comparing the time period necessaryto raise the moisture condition of said air flow downstream from saidfabric from said first moisture condition to said second moisturecondition with said fabric moisture test period while said air flow isbeing changed until said fabric is dry.

14. A method of controlling a fabric drying cycle by a dryer havingmeans for creating an air flow, means for reducing said air flow, meansfor sensing the dryness of said air flow and means for variably heatingcomprising the steps of, applying a reduced air flow and reduced heatingduring the first portion of said drying cycle, applying an increased airflow and an increased heating during a second portion of said dryingcycle, intermittently applying a reduced air flow and a reduced heatingto initiate each of a series of third portions of said drying cycle, andsensing a dryness of said fabric during said third portions of saiddrying cycle until said fabric is dry.

15. A method of controlling a fabric drying cycle by a dryer havingmeans for creating an air flow, means for reducing said air flow, meansfor sensing the dryness of said air flow and means for variably heatingcomprising the steps of, applying an unrcduced air flow and an unreducedheating during a first portion of said drying cycle, intermittentlyapplying a reduced air flow and a reduced heating to initiate each of aseries of second portions of said drying cycle, and sensing a dryness ofsaid fabric during said second portions of said drying cycle until saidfabric is dry.

16. In combination with a dryer having means for producing air flowthrough said dryer, controllable means for heating said air flow, meansfor restricting said air flow and means for sensing a moisture conditionof said air flow on the exhaust side of said dryer, means forcontrolling said restricting means to reduce said air flow in responseto a predetermined decreased moisture condition sensed by said sensingmeans, means actuated concurrently with said control means forinitiating a variable moisture condition test period operable betweensaid predetermined decreased moisture condition and a predeterminedincreased moisture condition when said control means reduces said airflow, and means for terminating said drying when said sensing meanssenses a condition of no free moisture throughout said test period.

References Cited in the file of this patent UNITED STATES PATENTS2,170,763 OhlsOn Aug. 22, 1939 2,741,856 Hall Apr. 17, 1956 2,775,047Morrison Dec. 25, 1956 2,819,540 Toma et a1 Jan. 14, 1958 2,820,304Horecky I an. 21, 1958 2,851,789 Dunkelman Sept. 16, 1958 2,863,224Zehrbach Dec. 9, 1958 2,895,230 Reiley July 21, 1959 2,970,383 HughesFeb. 7, 1961 3,028,680 Conlee Apr. 10, 1962 FOREIGN PATENTS 225,397Australia Apr. 30, 1959

12. AN ARRANGEMENT FOR CONTROLLING A DRYER IN A DRYING CYCLE FOR MOISTFABRIC COMPRISING, MEANS FOR INITIATING THE DRYING OF SAID MOIST FABRIC,MEANS FOR SENSING PREDETERMINED FIRST AND SECOND MOISTURE CONDITIONSLEAVING SAID FABRIC BEFORE SAID FABRIC IS DRY, MEANS ACTUATABLE AFTER ADELAYED INTERVAL IN RESPONSE TO THE SENSING OF SAID PREDETERMINED FIRSTMOISTURE CONDITION BY SAID SENSING MEANS FOR SELECTING A FABRIC MOISTURETEST PERIOD VARIABLE IN DURATION IN ACCORDANCE WITH THE TIME ELAPSEDBETWEEN THE INITIATION OF SAID DRYING AND THE SENSING OF SAID FIRSTMOISTURE CONDITION, AND MEANS FOR REPEATEDLY COMPARING THE TIME PERIODNECESSARY TO RAISE THE MOISTURE CONDITION LEAVING SAID FABRIC FROM SAIDFIRST MOISTURE CONDITION LEAVING MOISTURE CONDITION WITH SAID FABRICMOISTURE TEST PERIOD UNTIL SAID FABRIC IS DRY.